Hot-wire reticule



Oct. 27, 1 959 I KQLLMORGEN EIAL 2,909,838

HOT-WIRE RETICULE Filed Oct. 4, 1956 ERNST O.KOLLMORGEN HARRY D.WINTLE,JR.

THEIRATTORNEYS I l INVENTORS My 5 United States Patent HOT-WIRE RETICULE Ernst Otto Kollmorgen, Amherst, and Harry Drayton Wintle, Jr., Florence, Mass., assignors to Kollmorgen Optical Corporation, Northampton, Mass., a corporation of New York Application October 4, 1956, Serial No. 613,854

4 Claims. (Cl. 33-50) This invention relates to improvements in optical sighting instruments and, more particularly, to a reticule for use in optical instruments, such as telescopic rifle sights.

The reticule commonly used in rifle sights includes cross hairs which are used to aim the rifle. The target at which the rifle is aimed is located at the intersection of the cross hairs. Obviously, therefore, it is essential that the cross hairs be visible against the target.

The present invention relates to improvements in the reticules for telescopic sights wherein the reticule can be illuminated for use at night or under other conditions of extremely poor illumination. Whereas only the intersection of the cross hairs is used to locate the target at which the rifle is aimed, it is highly desirable to have this point of intersection visible against a poorly illuminated target. To accomplish this, the present invention employs a reticule comprising a pair of wires forming a symmetrical cross. The reticule is located at some focal plane in the optical system, such as the principal focus of the objective lens in the telescopic rifle sight. The wires are heated by the passage of a small electric current therethrough which causes them to glow. Since only the point of intersection is used in aiming the rifle the electric current may be adjusted until the cross wires glow only at their intersection.

Accordingly, it is one object of the present invention to provide an improved method and apparatus for rendering the intersection of cross hairs in a reticule visible against a dark target.

A further object of the present invention is to provide an improved method and apparatus for improving the efiectiveness of a reticule under conditions of poor il lumination.

For a more complete understanding of these and other objects of the present invention, reference may be had to the description which follows and to the accompanying drawings in which:

Figure 1 is a longitudinal view, partly in cross section, of an optical sight instrument embodying the present invention;

Figure 2 is a perspective view of the reticule illustrating one embodiment of the present invention.

Referring to Figure 1, the telescopic sight may be of any type such as, for example, those forming the subject matter of copending applications, Serial Nos. 481,090 and 530,526, each assigned to the assignee of the present invention. The reference numeral refers generally to the telescopic sight in which the reticule 13 may be mounted by any suitable means. Electrical insulating material 14 insulates the reticule from the surrounding mount.

Referring now to Figure 2 which illustrates the principle of the present invention, 16 refers to a base which is divided into two halves 17 and 18. Suitable insulating material 19 and 20 serves to electrically insulate each of the base halves 17 and 18 from the other. Two slots 21 and 22 are located in the rim 23 of the base half 18 at approximately 90 apart and substantially diametri- Patented Oct. 27, 1959 cally opposite from corresponding slots 24 and 25 in the opposite base half 17. Cross wires 26 and 27 stretched between these slots will intersect perpendicularly at the center 28. One end of cross wire 26 is secured directly to the base half 18, and one end of cross Wire 27 is secured directly to the base half 17. The other end of cross wire 26 is secured to a spring 29, and the other end of cross wire 27 is secured to a spring 30. Springs 29 and 30 are secured to the base halves 17 and 18, respectively, by any suitable means. The purpose of the springs 29 and 30 is to maintain the respective cross wire taut when they are heated in a manner to be described in greater detail hereinafter. Of course, suitable springs may be located at both ends of each of the cross wires if desired.

One terminal 36 of an electric source, such as for example, a battery 31, is connected to the base half 18 by an electrical conductor 32. The other terminal 37 of battery 31 is connected to a current limiting resistor 33 by means of an electrical conductor 38. An electrical conductor 34 connects the slidable contact 35 of resistor 33 to the other base half 17 In operation, an electric current will flow from the terminal 37 of battery 31 through the conductor 38, resistor 33, slidable contact 35, conductor 34, base half 17, spring 29, cross wire 26, base half 18, conductor 32 to the terminal 36. Of course, there will be current flow through cross wire 27 in the direction from base half 17 towards base half 18, and since the two cross wires are in parallel, no short circuit will result if they should touch at the center 28. By adjusting the slidable contact 35, the current in the cross wires may be controlled to any desired degree.

Current flowing in the cross wires causes them to heat, which heat is dissipated into the surrounding air. The rate of heat dissipation from the cross Wires will be the lowest at the region of their mutual intersection 28, since both wires are contributing to the ambient temperature in this region. more brightly at this intersection 28. By adjusting the slidable contact 35, the electric current in each wire 26 and 27 can be so controlled as to produce a visible glow in each wire for only a very short distance on each side of this intersection 28, for example, a distance of approximately 0.015 inch each side of the intersection. Since only the intersection of the cross wires is used for sighting purposes, the glow at this point is the most significant. The absence of any illumination throughout most of the length of each wire 26 and 27 is of considerable advantage in that it results in the least possible disturbance of the darkness-adaptation in the observers eye.

In one embodiment of the present invention, and for illustration purposes only, platinum-iridium wire may be used in the approximate proportions Pt10% Ir. The diameter of each wire may be in the order of 0.001 inch and a length of approximately one-half inch. For such material, if a battery source of three volts is used, the current flow will be approximately 0.5 ampere. Variations in the applied voltage permit control of the heat in the cross wires to lower or higher temperatures, as may be dictated by the brightness of the object aimed at and by the degree of brightness-adaptation of the observers eye.

The invention has been shown by way of example only, and many modifications and variations may be made therein Without departing from the spirit of the invention. While the illuminated reticule described herein is particularly adaptable to telescopic rifle sights, it will be understood that such a reticule may be used in other types of sighting instruments. Therefore, it is understood that the invention is not to be limited to any Consequently, the wires will glow' specified form or embodiment except insofar as such limitations are set forth in the claims.

We claim:

1. A reticule comprising electrically conductive cross wires of uniform dimensions, insulation means to electrically insulate two adjacent ends of said cross wires from the opposite adjacent ends, means to support said cross wires in a gaseous atmosphere, and electric source means connected to said cross wires to cause said cross wires to grow only at the point of intersection.

2. A reticule comprising a base divided into first and second portions, insulating means to electrically insulate said first base portion from said second base portion, a first cross wire secured at one end to said first base portion and at the opposite end to said second base portion to support said first cross wire in a gaseous atmosphere, a second cross wire secured at one end to said first base portion and at the opposite end to said second base portion to support said second cross wire in a gaseous atmosphere, and electric source means connected to said cross wires to cause said cross wires to glow at the point of intersection.

3. A reticule comprising a base divided into first and second portions, insulating means to electrically insulate said first base portion from said second base portion, a first leaf spring mounted on said first base portion, a second leaf spring mounted on said second base portion, a first cross wire secured at one end to said first base portion and at the opposite end to said second leaf spring to support said first cross wire in a gaseous atmosphere, a second cross wire secured at one end to said second base portion and at the opposite end to said first leaf spring to support said second cross wire in a gaseous atmosphere, electrical source means connected to said first and second cross Wires to cause said cross wires to glow at the point of intersection, and a current limiting means to control the current flow in said cross wires.

4. A reticule comprising a pair of electrically conductive wires of substantially uniform cross-section in substantially right-angular relation, said wires being free from engagement with each other in a gaseous atmosphere and crossing at approximately their mid-points, means connecting said wires in parallel with a source of electrical energy, and means interposed between said source of electrical energy and said wires for adjusting the flow of electrical energy to cause said wires to glow only at their mid-points.

References Cited in the file of this patent UNITED STATES PATENTS 848,757 Lomb et a1. Apr. 2, 1907 2,162,723 Karnes June 20, 1939 2,752,435 Kalmus et al. June 26, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,909,838 October 27, 1959 Ernst Otto Kollmorgen et al It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 12, for "Wire" read Wires column 3, line 10, for "grow read glow Signed and sealed this 22nd day of March 1960.

(SEAL) Attest:

KARL H, AXLINE ROBERT C WATSON Attesting Officer Commissioner of Patents 

